Is the glass half full, or half eaten?

But now the professional drinking glass swallowers have asked why I didn’t give them the same sort of plug, and they have a point. This is another form of entertainment that brings joy to millions.

What I don’t understand, though, is how you find out if you’re good at this, how you determine exactly how big a glass you can handle, and above all, what you do when you suddenly realize you probably should have stopped with a glass that was one size smaller.